1. Field of the Invention
The present invention relates to a method of obtaining and merging volumetric data and surface data of a patient's dentition for use in designing and/or manufacturing a prosthodontic component, such as a drill guide, implant, or other prosthodontic appliance, for example.
2. Description of the Related Art
Dental implants are commonly used as anchoring members in prosthodontic restorations to provide prosthetic teeth at one or more edentulous sites in a patient's dentition at which the patient's original natural teeth have been lost or damaged. Typically, known implant systems include a dental implant made from a suitable biocompatible material, such as titanium. The dental implant is typically threaded into a bore which is drilled into the patient's mandible or maxilla at the edentulous site. The implant provides an anchoring member for a dental abutment, which in turn provides an interface between the implant and a dental restoration. The restoration is typically a porcelain crown fashioned according to known methods to replicate the shape of the tooth being replaced.
Many dental implant surgeries are performed in two stages. In the initial or first stage, an incision is made in the patient's gingiva at an edentulous side, and a bore is then drilled into the patient's mandible or maxilla at the edentulous site, followed by threading or impacting a dental implant into the bore using a suitable driver. Thereafter, a cap is fitted onto the implant to close the abutment coupling structure of the implant, and the gingiva is sutured over the implant. Over a period of several months, the patient's jaw bone grows around and/or into the implant to securely anchor the implant in the surrounding bone, a process known as osseointegration.
In a second stage of the procedure following osseointegration, the dentist surgically reopens the gingiva at the implant site and secures an abutment and optionally, a temporary prosthesis or temporary healing member, to the implant. Then, a suitable permanent prosthesis or crown is fashioned, such as from one or more impressions taken of the abutment and the surrounding gingival tissue and dentition. In the final stage, the temporary prosthesis or healing member is removed and replaced with the permanent prosthesis, which is attached to the abutment with cement or with a fastener, for example.
If the patient has a site at which more than one tooth is missing, multiple implants may be used to provide anchorage for a denture bar, a bridge, or other prosthodontic appliance.
To drill holes in the jawbone of a patient, an oral surgeon may use a drill guide, which is typically formed as a custom appliance that overlays the drill site and at least a portion of the surrounding gum tissue and/or dentition. The drill guide includes a hole aligned along the intended drill axis, and one or more removable drill guide tubes may be positioned within the drill guide hole to allow drills of different diameters to be used in succession for drilling the holes in the jawbone in which the implants will be secured.
The drill guide may be fabricated based on a physical model of the patient's dentition, or may be designed based on scan data obtained of the patient's dentition.
In one procedure, an impression is taken of a patient's dentition during a first visit to the clinician. Then, at a dental lab, a physical model is made of the impression, and a waxed-up tooth or teeth may be made on the physical model at sites in which a patient's tooth or teeth are missing. In an edentulous patient, impressions may be taken of both the patient's existing dentures and of the patient's gum tissue without the dentures. Then, at the dental lab, a scan stent is made based on the impressions and/or the physical model. A least a portion of the scan stent typically corresponds to the patient's bite registration, and the scan stent also may include one or more structures corresponding to the waxed-up tooth or teeth. In an edentulous patient, the scan stent itself may resemble the patient's dentures.
The scan stent further includes radio-opaque markers that will appear in a radiographic scan, such as a computed tomography (CT) scan. A physical model scan is then obtained of the physical model with the scan stent placed on the physical model to generate image data corresponding to the exterior surfaces of the patient's teeth, soft tissue and gums. Then, the scan stent is shipped back to the clinician.
In a second visit to the clinician, the scan stent is placed within the patient's dentition, such as by fitting the stent directly on the patient's teeth or gums, or by the patient capturing the stent in between the patient's teeth, for example. A CT scan is then taken of the patient's dentition with the stent. The CT scan generates an image of the patient's jaw bone(s), teeth, and some of the surrounding soft tissue. However, in most cases in which the patient has had prior dental work, for example, the patient's amalgams, existing implants, or other metal structures cause scattering in the CT scan image such that the CT scan threshold must be set such that the CT scan only develops information corresponding to the jaw bone(s) and some of the surrounding soft tissue of the patient.
Therefore, in order for the clinician to properly plan the treatment, and for the lab technician to properly design the drill guide or other prosthodontic appliance, the images from both the physical model scan and from the anatomical CT scan must be merged to generate a combined image of the patient's dental condition that includes a more complete representation of the patient's bone, soft tissue, and teeth.
The radio-opaque markers of the scan stent that appear in each of the two scan images are used by suitable software to merge the scans, and a drill guide or other prosthodontic appliance is designed from the merged data.
Also, in many cases, a clinician may obtain a first, diagnostic CT scan of a patient in order to determine a treatment plan and, if the clinician determines that the patient is a good candidate for a suitable prosthetic appliance, the clinician will proceed as outlined above, including generating a later, second CT scan with the scan stent in place. Disadvantageously, this procedure requires two CT scans to be taken.
What is needed is a method that is an improvement on the foregoing.